Valves for vapour compression systems such as refrigeration systems or heat pump systems are known in different structures and for different uses within the refrigeration system. Mostly, valves of refrigeration systems are thermo-statically or electro-mechanically operated, depending on use within the refrigeration system. Shape Memory Alloy (SMA) material has also been used for operating a valve.
WO 2010/142997 discloses a valve comprising a body, a passageway, a sealing member, a trigger, and a temperature responsive trigger actuator. The temperature responsive trigger actuator includes a plurality of point trigger actuator portions wherein each one of the plurality of point trigger actuator portions is characterized by a respective shape-changing temperature and is configured such that, for each one of the plurality of point trigger actuator portions, when the temperature of the point trigger actuator portion is below the respective shape-changing temperature, the point trigger actuator portion is disposed in a respective low temperature shape condition, and when the temperature of the point trigger actuator portion is at or above the respective shape-changing temperature, the point trigger actuator portion is disposed in a respective high temperature shape condition. WO 2010/142997 uses one wire strip extending from a position distant from the sealing member, into the body to a position proximate the sealing member, using a force from the one wire strip for triggering the sealing member and using part of the valve body for conducting electrical current to the trigger actuator.
U.S. Pat. No. 5,345,963 discloses an electrically controlled modulating pressure regulator in which a main valve regulates fluid flow between an inlet and an outlet in response to a control pressure produced by a servo valve which is responsive to the outlet pressure and the force applied by a regulator spring to a diaphragm carrying the servo valve closure element. Deformation of the regulator spring can be varied by an electrical actuator in the form of a wire segment of a shape memory alloy through which electric current can be passed to vary its temperature and length. An adjustable spring retainer electrically controlled by an actuator including a wire segment of a shape memory alloy material. Ends of wire segment are fixed with respect to a housing. Either the wire segment passes over the end of a push rod assembly, which extends between the intermediate location on the wire segment and spring retainer 43, or a compression spring is positioned between a first spring retainer on the top side of a diaphragm and a second spring retainer, whose position can be electrically varied by means of actuator comprising a wire segment of a shape memory alloy material regulator compression spring 101. The wire segment operates a valve element in a manner, so that the wire segment itself is out of contact with the fluid flow passing through the pressure regulator.
US 2002/171055 discloses an SMA actuated miniature latching valve for on and off control of fluid flow. A valve closure includes a poppet for opening and closing the fluid flow path. The poppet is operated responsive to an actuator mechanism which has SMA wires arranged to be actuated by electric resistant heating. Actuation causes different ones of the wires to contract and pull the poppet either toward or away from a valve seat. A latching mechanism comprising a conical spring operates between two bistable positions which hold the poppet either fully open or fully closed without further application of power to the actuators. First actuator 50 is comprised of a pair of shape memory alloy wires. The two wires are mounted at their upper ends to a bracket which is attached to the upper end of a mid-housing. The lower ends of these two wires are attached to a drive bar which is attached to the lower end of an elongate tubular pintle sleeve which fits about a pintle. The two SMA wires are actuated by being heating through their phase change transition temperatures so that they revert to their memory shapes. This causes them to contract in length so that they act in unison to exert an upward pulling force on the pintle sleeve, causing the pintle to slide up. The pintle in turn moves a poppet up to the valve open position. SMA wires operate a pintle, so that he wires themselves are out of contact with the fluid flow passing through the pressure regulator.
It may be an object of the present invention to provide an actuator making use of Shape Memory Alloy, and which actuator may function in a valve for a vapour compression system, even if high pressure differences are present in the valve body and even if the Shape Memory Alloy is passing fully or partly through part of the valve, where also a fluid is passing through the valve or if the actuator of the valve is surrounded fully or partly by an environment having a certain temperature not suited for Shape Memory Alloy. It may also be an object to provide a valve, where there is an easy way of providing a normally open or normally closed position. Furthermore, it may be an object of the invention to provide a valve for a refrigeration system or a heat pump system, where Shape Memory Alloy properties are maintained, when refrigerant is flowing through the valve.